This invention relates generally to chain-connecting tools and more specifically to screw-type chain tighteners for use in connecting together the ends of roller chains.
Roller chains are widely used in lumber-handling machinery in lumber mills. Due to the heavy loads to which they are subjected, such chains frequently break. As a result of constant usage in an adverse environment, they also tend to wear out very quickly. Consequently, such chains require frequent maintenance, repair and replacement.
Repair of roller chains in lumber-handling machinery can be extremely difficult. Such chains are frequently positioned in very awkward locations. Sometimes multiple roller chains are positioned side by side, very closely together. Their lengths can range from very short to very long, for example, from four or five feet in length to dozens of feet or longer. In the case of very short chains, their sprockets are positioned closely together along the length of the chain. Longer chains may be positioned in narrow guideways or behind protective shields which are not always removable to gain access to the chain. Many different sizes of chains are used in a typical sawmill, and sometimes in a single piece of lumber-handling equipment.
Such an environment imposes rather stringent requirements on any tools that might be used in repairing roller chains. The great length of some chains requires a tool capable of stretching such chains over a long distance. The short length of other chains requires a tool capable of fitting into short distances between the sprockets on which such chains are mounted. Close lateral spacing between the chains or placement in guideways, behind guard shields, or simply in hard-to-reach places, can make it very difficult to position tools on the chains to rejoin their ends. Finally, the common use of different size chains frequently necessitates the use of different-sized tools.
It would be desirable to have a single tool usable to connect both long and short roller chains of differing gauges. It should be positionable on chains in narrow guideways or behind guard shields and yet short enough to fit lengthwise between closely spaced sprockets. Existing chain tighteners and positioning tools meet some of these requirements, but none meets all of them.
U.S. Pat. No. 752,074 to Jackson discloses a chain tightener designed for use in repairing bicycles and early model chain-drive cars. This tool employs a pair of opposed jaw heads interconnected by parallel, oppositely-directed shafts, each fixed in one head and extending through a bore in the other head. A wing nut is threaded on one shaft for advancing one head toward the other. On one side of the jaw heads is mounted a pair of large jaws or hooks for large roller chains. On the other side is a pair of small hooks for engaging small chains. This tool has many disadvantages. The oppositely-directed rods make it overly long for use with very short chains. The wing nut cannot retract the heads to initially position them on the chain. The wing nut must also be turned manually, not only because its shape will not fit a wrench, but because the threaded rod protrudes through it, precluding use of a socket wrench. The unthreaded rod is needed to keep the heads parallel while tightening a chain, but makes it difficult for this tool to fit into very narrow spaces, such as along a guideway or behind a chain guard shield. Provision for separate pairs of chain hooks to fit two different sizes of chain makes the tool even more cumbersome.
U.S. Pat. No. 1,994,270 to Cetrano discloses another form of tool for use in repairing chains. This tool has a pair of block-shaped slides. A square shaft or bar extends through the slides, each of which mount four chain hooks, one on each side of the block. A lever-actuated camming lobe is pivotally-mounted on each end of the shaft in position to move the slides together. Obviously, this tool is not readily usable in close spaces where the levers cannot be worked. In addition, the radii of the camming lobes limit the amount by which a chain can be stretched. Long chains frequently must be stretched more than this tool is capable of stretching them.
U.S. Pat. No. 2,950,899 to Wilson discloses an H-shaped, lever-type chain-positioning tool comprising a pair of levers pivotally connected to a cross bar. A pair of opposed chain hooks are mounted on two adjacent ends of the levers. A screw extends parallel to the cross bar through the opposite ends of the levers. Half-lengths of the screw are threaded in opposite directions for moving the hooks in opposite directions when the screw is rotated. This tool requires more space than is often available in lumber-handling equipment. Like the Cetrano tool, it has a limited range of operation to stretch a chain. To stretch a very long chain, one of the levers must be repositioned on the cross bar. This procedure requires dismantling and reassembling the tool, which is time-consuming and risks loss of tool parts.
Tools for use in repairing tracks on track-type vehicles, such as combat tanks and crawler tractors, are also known. U.S. Pat. No. 2,382,447 to Schaeufele discloses a track maintenance tool comprising a pair of parallel side plates connected at adjacent ends by end blocks. A screw journaled in one end block extends lengthwise between the parallel side plates and is threadedly received in an internally-threaded sliding block. A hook shaped to engage a track pin is mounted on the sliding block. A second such hook is mounted on the end block adjacent the free end of the screw. Rotation of the screw moves the slide block along the slide plates to tighten the track. The lateral sides of the sliding block are channeled to slidingly receive the slide plates. This arrangement is required to keep the hooks parallel and avoid bending the screw while tightening the track, but necessitates precision machining. This arrangement also prevents relative rotation of the hooks which would be disadvantageous in a roller chain-connecting tool because it would limit the ability to maneuver the tool in a very tight location for positioning the hooks in a roller chain. The journaled end of the screw carries a ratchet and a pawl lever is pivotally mounted thereon for turning the screw. Detachable wrenches cannot be used with this tool. Moreover, the screw can only be turned from one end, which is disadvantageous when working in inaccessible places.
Other related devices are disclosed in U.S. Pat. Nos. 949,458; 1,929,026; 2,387,551 and 2,818,229. Two forms of clamp are disclosed in U.S. Pat. Nos. 442,733 and 3,425,098. However, such devices are either altogether unsuited for connecting the ends of roller chains or suffer from the deficiencies of one or more of the tools discussed in greater detail above.
None of the foregoing patents discloses an all-purpose chain-tightening and connecting tool usable on both long and short chains of both light and heavy gauge and yet positionable and operable in very tight places. Accordingly, a need remains for a single, all-purpose chain-connecting tool meeting these requirements.